Process for halogenation of organic compounds



SR OGGI bll HUU `April zo, 1937.

w. ENGS Er AL 2,077,382

Y PROCESS FOR HALOGENATION OF' ORGANIC COMPOUNDS Wa/ar Filed Oct. 7,1935 From Sforagc krmome/er /5 Prod/ff Coo//ng Waferzou. bnlwub HY,UAHUUN COMPOUNDS..A

Patented Apr.

UNITED STATES DeaTCH HOO.

PATENTA OFFICE PROCESS FOR vHALOGENATION F ORGANIC COMPOUNDS WilliamEngs and Arthur Redmond, Berkeley,

Calif., assignors to Shell Development Company, San Francisco, Calif., acorporation of Delaware Application October 7, 1935, Serial No. 43,947

20 Claims.

This invention is concerned with an improved process for carrying out,on an industrially practical scale, the halogenation of organiccompounds via substitution. It provides a novel method of greatflexibility and ease of control whereby the undesirable side reactionsusually accompanying such halo-substitutions, especially reactionsbetween the hydrogen halide formed and the desired product and/or anyunsubstituted starting material present, may be substantially entirelyeliminated, or very greatly reduced in extent, thereby improving theyields of the desired end-products.

The halogens may react with most organic compounds, especiallyunsaturated organic compounds, in a number of different Ways. Even Whenthe conditions of reaction are adjusted so that one type of reaction,for example, substitution, is substantially favored over halogenaddition or other types of reaction, it is still diflicult to obtainhigh yields of individual products because of the formation of highersubstitution products unless the organic compound used as startingmaterial is present in substantial excess of the stoichiometricrequirement for reaction with the halogen. In spite of this precautionthe yield of desired product, based on the organic compound consumed,may still be commercially impractical due to reaction between the excessstarting material and the halogen acid formed in the substitutionreaction. A further source of loss in yield may result from reaction ofthe desired halogen substituted product with the halogen acidsimultaneously produced.

We have found that these losses may be best avoided by prompt removal ofthe halogen acid substantially as fast as it is formed by treatment ofthe reaction mixture with a suitable halogen acid solvent, preferably asolvent which is substantially immiscible with the organic compoundbeing treated and most preferably also substantially immiscible with thedesired halogen substituted product. To this end We have found itusually most advantageous to pass the organic compound under treatmentand halogen or a compound yielding halogen under the reaction conditionsthru a reaction zone, maintained at` a temperature favoring halogensubstitution, directly into contact with the halogen acid solvent,preferably in the form of a spray or the like, whereby the halogen acidis separated from any unsubstituted starting material present and thenremove the halogen acid containing solvent from further contact with thehalogen substituted orvent introduced may also serve to condense theproduct Where the reaction is carried out in the vapor phase. Our novelprocess has the further advantage of making the recovery of by-productfree halogen acid a very simple procedure.

While our improved method may be applied to all organic compoundscapable of halogenation by substitution such as hydrocarbons, ketones,aldehydes, esters, organic acids, and the like, whether aliphatic,aromatic, carbocyclic or heterocyclic, it has particular advantage inthe production of halo-substituted unsaturated compounds Wherecliiiiculties due to side-reactions, particularly halogen acid additionreactions, are especially acute. Therefore, for the purpose of makingour invention more clear it will be described with more specificreference to the manufacture of such products, particularly chlorinatedunsaturated compounds.

Suitable starting material which may be used for the manufacture ofunsaturated halogen containing compounds in high yields by our improvedmethod include unsaturated alkyl, aralkyl, and alicyclic compoundscontaining one or more olenic linkages and embracing besides theunsaturated hydrocarbons, theirsubstitution and addition products whichcontain at least one double bond. The following list shows some of thetypes of compounds to which our process can be applied with particularadvantage:

CH3 CH:

O-om-on--on-pm. ew,

Such .compounds may be used in a pure state, eitheras'individualunsaturated compounds or as mixtures of the pure compounds,or in admixture with parafns or other saturated materials which may ormay not undergo simultaneous reaction. The source of the unsaturatedcompound or unsaturated compound containing mixture used is immaterial.When working with olefines,.

for example, they may be derived from mineral oils as petroleum,petroleum products, shale oil, and the like, or from natural gas, orcoal, peat, pitches and like or related carboniferous natural material,as well as from animal and vegetable oils, fats and waxes. The oleflnespresent in such starting material may be of natural occurrence, theresult of pyrolytic treatment or cracking, or a product of a destructivehydrogenation treatment. Furthermore, such olefines may advantageouslybe used in the form of hydrocarbon fractions consisting of, orpredominating in, hydrocarbons containing the same number of carbonatoms to the molecule, as a propane-propylene cut, a butane-butyleneout, a pentane-pentylene cut, etc. Alternatively the oleiine or oleiinesused as starting material may be obtained by the dehydration ofalcohols.

The conditions of halogenation are preferably adjusted to the nature ofthe unsaturated compound or compounds undergoing treatment and thehalogenation agent employed, so that the desired degree of halogensubstitution is promoted while halogen addition is suppressed. Withthose unsaturated compounds wherein a double bond joins two carbon atomsone of which is linked to three carbon atoms, such as tertiary-baseolenes, e. g., isobutylene, tri-methylethylene, unsymmetrical methylethyl ethylene, tertiary hexylenes, and the like, halogen substitutiontakes place in preference to addition even at quite low temperatures inthe absence of an excess of halogen. With open or closed chain compoundsof an aliphatic character possessing other types of double linkages,such, for example, as ethylene, the secondary base olefnes as propylene,a and ,S butylene, a and amylene, etc., cyclohexene, and the like,temperatures of halogenation above 100 C. especially between about 200C. and 500 C., are necessary in order to promote substitution ratherthan addition. In such cases in general the higher the temperature the-more unsaturated halide is formed, while the addition of halogen to thedouble bond or bonds is suppressed, but in any case the reactiontemperature is preferably maintained below those temperatures at whichpolymerization and/or cracking of the unsaturated compounds are favoredunder the prevailing space velocities, pressures and degree of dilution.

In view of the'high reaction velocity of free halogen with unsaturatedcompounds, even at low temperatures, it is preferable to preheat thereactants separately if reaction temperatures are desired which arehigher than would be obtained by the heat of the reaction proper.Heating of the reaction zone alone is not very effective because if thecold reagents enter the reaction zone they will have at least partlyreacted via addition of halogen and/or halogen acid before they areheated to the desired temperature at which substitution is favored. Incarrying out our invention, we preferably heat the unsaturated organiccompound to the desired reaction temperature and then introduce the freehalogen, when such is employed. It is usually desirable to make use ofconsiderable amount of halogenation takes place.

While, in most cases, we prefer to have the molal ratio of availablehalogen to unsaturated compound not exceed 1 to 1 so that we obtain apreponderance of monohalogen substitution product, we may employ ahigher ratio and obtain a higher degree of halogen substitution, such asa dior trichloride which will still be unsaturated, by proper control ofthe reaction temperature. More preferably, however, we operate with anexcess of unsaturated compound over the stoichiometrlc requirement forreaction with the available halogen. For the preparation ofmono-chlorinated oleflns about 1.25 to about 1.75, preferably about1.50, mols of oleiine per mol. of free chlorine gives eiicient results.The chlorine may be introduced at high velocity at a plurality ofseparated points along the reaction tube while the material beinghalogenated is maintained within the desired range of reactiontemperature. This is -a particularly useful method for the preparationof unsaturated products of higher halogen content than themonosubstituted form since the ratio of free halogen to unsaturatedcompound may be maintained substantially at the optimum at all times,and yet any desired degree of halogenation may be effected with safetyin a singley operation.

Any of the known halogenation catalysts, such as halides of iron,antimony, tin, phosphorous, aluminum, etc., or metallic iron, or sulfuror active carbon or the like may be used to accelerate the halogensubstitution. The reaction may also be accelerated photochemically bythe use of reaction tubes of silica or glass which permit the passage oflight of effective wave lengths and exposure to sunlight or ultra-violetor other rays from suitable light-giving devices. If desired, aplurality of reaction accelerating expedients may be used, such as heatand light, or heat and catalyst, or heat, light and catalyst. Ingeneral, the temperature of the reaction may be lowered if a catalyst oreffective light is used to accelerate the reaction.

Inert diluents, such as nitrogen, etc., may be added with the reactantsand utilized for their capacity to absorb heat. overheating may beprevented by conventional cooling means or by the evaporation of aninternal cooling agent, which may be an excess of the organic compoundbeing treated for example, and/or a lower boiling hydrocarbon or thelike, so that there is instantaneous dissipation of the reaction heatuniformly thruout the reaction mixture. Oxygen may be added as aninhibitor of the substitution reaction of saturated organic compounds,as paraflin hydrocarbons, where such are present with the unsaturatedorganic compound being treated.

The reaction may be carried out with the organic compound in either theliquid or gaseous' state. Either intermittent, batch or continuousmethods of operation may be employed and unrea'cted starting materialmay be advantageously recycled to the reactor to increase conversions.

However the halogen substitution reaction is carried out, it is onlyessential to our invention zaztHlMls-TRY, Clissoni C-OMPouNns.

that the minimum contact time for the desired degree ofA reaction beprovided and that subsequent reaction be promptly inhibited by treatmentof the reaction products with a solvent for the halogen acid formed.Prior attempts to accomplish the same end by sudden cooling of thereaction mixture have been unsuccessful because of the high reactivityof the halogen acids, especially with unsaturated organic compounds,even at low temperatures. Processes involving separation of the halogenacid from the reacted mixture by fractionation lead to even moreextensive secondary reaction and we have found that only by replacementof fractionation by a quenching of the secondary reactions by scrubbingout the halogen acid with a suitable solvent, may commerciallyeconomical yields of the desired end product be attained.

While any suitable halogen acid solvent may be applied in our process,we have found that one of the most effective is water not only becauseof its high solubility for vthe halogen acids and substantialimmiscibility with most halogenated organic products but also because ofits high heat capacity and latent heat which make it an effectivecooling agent when used in small amounts so that undue dilution of thehydrochloric acid may be avoided. Other suitable media for effecting theprompt removal of halogen acid from the reaction mixture include aqueoussalt solutions such as brineland the like, or aqueous alkaline solutionsor dilute solutions of acid unreactive with the organic compound beingtreated and the desired halogen substituted product. Still othersuitable solvents may be used.

The method of applying the chosen halogen acid solvent may vary widelydepending upon the method of carrying out the halogen substitution andon the nature of the organic compound being halogenated and of thedesired end-product. Thus where high boiling compounds are being treatedbatch-wise in the liquid phase it may sometimes be feasible to introducethe halogen acid solvent directly into the reaction mixture withstirring, for example, to promote intimate contact of the phases andthen promptly remove the resulting acid solution during the reaction. Incontinuous methodsof operation on the other hand, it is usually moreadvantageous to provide a separate solvent treating zone in directcommunication with the halogenation zone to which the reactants may bepassed as rapidly as reacted and in which they may be intimatelycontacted with the halogen acid solvent so that the acid may be promptlywithdrawn from reaction. To this end resort may be had to spraytreatment, or counter current scrubbing of the reacted mixture, in emptyor preferably suitably packed towers, or other conventional methods ofpromptly extracting the halogen acid.

The amount of halogen acid solvent which will `be required in any givencase will be influenced by the method of operation, the degree ofcooling of the reaction product which it is desired to impart thereby,etc. In general, it is inadvisable to use such small amounts of solvent,or to recirfculate solvent containing free acid to such an extent thatthe acid solvent solution becomes substantially reactive with thedesired product and/ or any unreacted starting material present. In thechlorination of unsaturated olenes, for example, it has been found thataqueous hydrochloric acid solutions of around 20% or more areundesirable as they tend to cause the forma- UUUI Ul' wwwmwa-; aovzssa 3tion of excessive amounts of saturated dichlorides even at ordinarytemperatures.

As one example of a method of applying our invention, reference may behad to the accompanying drawing which shows diagrammatically a preferredassemblage of apparatus adapted to the manufacture of methyl allylchloride.

Isobutylene, or a mixture containing isobutylene. for example, a.butanebutylene fraction from cracked petroleum oil, in either the liquidor gaseous state, the liquid state being preferred as it gives somewhathigher yields, is fed from a storage vessel, not shown, thru valvecontrolled pipe line I and metering device 2, to a preheater 3 (whichmay be omitted when it is desired to add the isobutylene in the liquidphase) and thence to a branched tube 4 where it comes into contact witha stream of chlorine from cylinder 5. The flow of chlorine is measuredby orifice meter 6 and controlled by valves 'I and 8 prefo erably sothat about of a mol. of chlorine are introduced per mol. of isobutylene.Higher chlorine ratios may be used altho they are less desirable as theytend to favor formation of dichlorisobutane and dichlorisobutene, whilemolal chlorine-isobutylene ratios lower than about 2%; :1 are withoutappreciable effect except in so far as they reduce the capacity of theapparatus. The chlorine and isobutylene streams are advantageouslybrought together at an angle of about to promote rapid mixing, thechlorine being usually admitted as the side stream.

The mixed reactants pass thru a reaction tube 9 which may suitably bemade of Pyrex glass or other acid and heat resistant material, and whichpreferably is of such a volume that the average time of residence of thereactants therein is about 1 second. Contact times of the reactants inthe reaction zone of less than 1 second have been found to be sufficientfor completion of the reaction to form methyl allyl chloride but thereappears to be no measurable advantage in reducing the time below thatvalue. 'Somewhat longer reaction times may be permissible in certaincases altho they tend to lower the yield of methyl allyl chloride,particularly if times of 5 seconds or over are used increasing amountsof higher chlorinated products are formed. On substantial completion ofthe reaction in tube 9, the reactants are conducted at once to thebottom of a hydrochloric acid scrubbing tower I0 which mayadvantageously be made of tile pipe packed with ceramic 'rings or othersuitable filling which will pro- I I, with the reaction mixure. Thewater, or

equivalent HCl solvent, is admitted preferably at such a rate as willform about a 5 to 10% HC1 solution at the bottom of the column. Thescrubbing water not only absorbs the liberated hydrochloric acidpromptly stopping substantially all reaction thereof with the excessisobutylene present, but also condenses the methyl allyl chlorideproduced.

The unreacted isobutylene, together with butane and and butylene if abutane-butylene fraction has been used as starting material, passes tothe top of tower III from which it is run to a cooler I2, where it iscooled as vlow as possible to avoid losses of methyl allyl chloridewhich has a high vapor pressure. e The methyl allyl chloride sorecovered may be withdrawn thru valve controlled drain I3 and added tothe product. The aqueous hydrochloric acid and methyl allyl chloridecondensed in tower I0 may be run from the bottom thru an auxiliarycooler I4 to a separator Total chlorine Saponiiable chlorine Specicgravity 20/4 0.924 Bromine number 175.4 A. S. T. M. distillation I. B. P'70.2 C. 5% 71.2 C. 71.5 C. 50% 72.0 C. 90% 72.3 C. 95% 72.5 C.

The yields obtainable under various conditions oi operation are shown inthe following table:

A iiinx.

puried state, are often of greater economic signicance than the savingsin halogen, isobutylene in a concentrated form being more costly thanchlorine, for example. Our process is not only controlled with greatease to give high yields oi.' individual products but also may becarried out in simple, easily constructed apparatus.

While we have in the foregoing described in some detail the preferredembodiment of our invention and some variants thereof, it will beunderstood that this is only for the purpose of making the inventionmore clear and that the invention is not to be regarded as limited tothe details of operation described, nor is it dependent upon thesoundness or accuracy of the theories advanced as to the advantageousresults attained. On the other hand, the invention is to be regarded aslimited only by the terms of the accompanying claims, in which it is ourintention to claim all novelty inherent therein as broadly as ispossible in view of the prior art.

We claim as our invention:

1. In a process of halogenating, by substitution, an organic compoundcapable of reacting with By a similar procedure carried out at highertemperatures, preferably by preheating the olene to about 200 to 500 C.before its admixture with the chlorine, high yields of monohalogenatedunsaturated compounds may be obtained from propylene, 2-,butene, andhomologous secondary base olenes.

While the olenes and their partially halogenated derivatives have beenemphasized in describing our invention and some of the typical methodsof carrying it out, it will be obvious that our process may be appliedwith equal advantage to the halo-substitution of a Wide variety of otherunsaturated compounds of which allyl acetate, mesityl oxide, oleic acid,and the like are typical. Nor is o'ur invention limited to thehalogenation of unsaturated compounds since by obvious modication ofoperating conditions it may also be applied to the halo-substitution ofother organic compounds capable of reacting, under the usualhalogenation conditions, with the halogen acid formed. Thus, forexample, our invention may also be advantageously applied in thechlorination of paramn hydrocarbons, particularly paraffin Wax where theprolonged contact with HCl occurring in the usual methods causesextensive discoloration of the product,

It is thus evident that our process offers great advantage in thetechnical scale production of many different halogenated products. Byproviding for the prompt separation of reaction products which in priorprocedures have been allowed opportunity to react during cooling and/orfractionation treatments, important savings both in` halogen and organicstarting'material are realized. The saving in organic unsaturated com-75 pounds, particularly when such are used in a Chlorine Weight FreeYield feed Molal Isobutylene percent HC1 p'ds l ratio inlet ReactionU'gl connt of lsoblylene telra' 58125515 chloride water Pggt Iggt C12chlorine C. in the from on on har pggllilt sglggr chlorine isobutylene10 1. 39 132-143 14. 4 75. 0 4. G4 72 71 16 1. 74 143-147 2. 1 77. 5 3.48 77 77 16 1. 93 97-104 2. 0 78. 2 3. 1l 78 78 16 1. 86 about 0 l, 2.78. 8 3. 14 85 83. 5 30. 8 1. 68 about 0 1. 2 81. O 3. 81 89. 0 89.

the halogen acid formed and containing a-plurality of carbon atoms, thesteps of contacting the reaction products substantially as fast asformed with a substantially non-reactive solvent for the halogen acidproduced and separating the halogenated organic product from theresulting halogen acid solution whereby prolonged contact of halogenacid solution with other components of the reaction mixture is avoided.

2. In a process of halogenating by substitution an unsaturated organiccompound containing an oleinic linkage, the steps of contacting thereaction products substantially as fast as formed with a solvent for thehalogen acid produced and separating the resulting halogen acid solutionfrom the other components of the reaction mixture whereby prolongedcontact of halogen acid solution with other components of the reactionmixture is avoided. A

3. In a process of halogenating by substitution, an unsaturated organiccompound containing an oleiinic linkage, the steps of removing thehalogen acid formed from the substantially reacted mixture immediatelyupon issuance of said mixture from the reaction zone by extraction Witha. solvent for said acid which is substantially immiscible with theunsaturated organic compound, and recovering an unsaturated organichalide.

4. In a process of halogenating by substitution an unsaturated organiccompound containing at least one unsaturated structure of the classconsisting of alkene, cycloalgene and aralkene structures, the steps oftreating the reacted mixture substantially as soon as formed with asolvent for the halogen acid formed added in such an amount as will forma halogen acid solution of low reactivity with the unsaturated product.

260. CHEMISTRY, CARBON COMPOUNDS.

5. In a process of halogenating by substitution an unsaturated organiccompound containing at least one voleilnic linkage, the steps ofremoving the reaction jproducts from said chamber sub- 5 stantially asfast as formed and immediately cool- 13. In a process of chlorinating bysubstitution 5 ing the withdrawn mixture by direct contact an oleflne,the step of absorbing the hydrochloric with an aqueous solvent for thehalogen acid acid produced substantially as fast as formed in formed ofan acid concentration such as is not a spray of water and recoveringunsaturated orsubstantially reactive with the unsaturated or-` ganicchloride.

l0 ganic halide produced at the temperature to 14. A process ofchlorinating by substitution a 10 which the mixture is cooled. secondaryolene which comprises preheating said 6. In a process for thesubstantial monohalogen olene to a`tempe'rature above one hundreddesubstitution of an unsaturated organic compound grees centigrade butbelow that temperature at containing an olenic linkage, the step ofconwhich substantial degradation of the olene takes tacting the halogenacid produced substantially place under theY reaction conditions,admixing l5 as fast as formed with a solvent therefor which gaseouschlorine with the preheated oleiine, abhas a low solubility for theother components of sorbing the hydrochloric acid produced in the retliereaction mixture and recovering an unsatusulting reaction substantiallyas fast as formed rated organic halide. by means of a spray of water andrecovering un- 7. In a process for producing a chloro subsaturatedorganic chloride. '20 stituted olefine from the corresponding oleflne,15 A process of chlorinating by substitution a. the steps of removingthe primary products rapsecondary butylene Which ooInpIiSeS preheatingidly from the sphere of the reagent, substantially the secondary-butylene to about 200 to 500 C.,

d simultaneously separating the hydrochloric acid injecting gaseouschlorine into the preheated bu- 20 formed from reactive contact with theother comtylene at a velocity in eXceSS of that of darne prop- 25ponents of the removed mixture by absorption agation under the existingconditions, absorbing in asolvent therefor, and recovering an unsatuthehydrochloric aoid produced Substantially aS rated organic chloride. fastas formed by means of a spray of water and 8. In a process ofchlorinating by substitution recovering unsaturated butylene chloride.

an unsaturated organic compound containing an 16. In a process ofchlorinating by substitution 30 olefiFnic linkage, the step of reducingthe concena tertiary olelne, the Step 0f Separating the hytration of thehydrochloric acid formed in the redrochloric acid formed from the othercomponents action by addition of water to the reaction prodof thereaction mixture by absorption in water ucts substantially as fast asformed in such an Substantially as fast as formed and recovering ULamount that said acid no longer has power to subtertiary unsaturatedorganic chloride. 30 stantially add under prevailing conditions to the1'7- In a proceSS of ohlorinating iSobutylene by double bond of theunsaturated organic chloride Substitution. the Step of Separating thehydroprodueed, chloric acid formed from the other components 9. In aprocess of chlorinating by substitution of the reaction mixture byabsorption in water an unsaturated organic compound containing ansubstantially as fast as formed and recovering 40 olelnic linkage thestep of contacting the products methyl allyl chloride- Y of saidreaction substantially as fast as formed 18. A process of producingmethyl allyl Chloride with an aqueous solvent for the hydrochloric acidWhich comprises injecting Chlorine into a molal produced therein whichis substantially unreaceXoeSS of isobutyleney Contacting the reactiontive at the temperature of absorption with the unmixture within about 5seconds with suiiicient 4.5 saturated organic chloride also produced.Water to form a solution with the hydrochloric l10. In a process ofchlorinating by substitution acid produced of a hydrochloric acidconcentraan unsaturated organic compound containing an tion of less than20%, and recovering methyl olenic linkage the step of passing theproducts allyl Chloride. l

of said reaction substantially as fast as formed 19- AproceSS ofproducing methyl allyl chloride 50 into a hydrochloric acid absorptionsystem wherewhich comprises injecting a stream of gaseous in reactionbetween the hydrochloric acid and the chlorine into a stream of liquidisobutylene conunsaturated product is substantially suppressed. taininghydrocarbon1 passing the reaction IniX- 11. In'a. process ofchlorinating by substitution ture substantially on substantialcompletion of an unsaturated organic Compound containing an the ChlorineSubstitution reaction into a. hydro- 55 olenic linkage the step ofsubstantially dissipatchloric acid scrubbing toWer fed With Su-'icienting the heat liberated from the chlorination by water to substantiallycondense the methyl allyl treatment of the reaction productssubstantially Chloride formed and recovering from Said tower as soon asthey are formed with a sufiicient quanaqueous hydrochloric acid andmethyl allyl Chlotity of solvent for the hydrochloric acid producedride. 60

to form a hydrochloric acid solution substantially 20. In a proCeSS ofchlorinating a tertiary amylunreactive at the temperature to which thereene by substitution. the step of separating the action products `arecooled with the unsaturated hydrochloric acid formed from the othercomorganic chloride product. ponents of the reaction mixture byabsorption in 12. In aprocess of chlorinating by substitution watersubstantially as fast as formed and re- 65 an unsaturated organiccompound containing an olenic linkage the step of rendering thehydrochloric acid formed in the reaction substantially non-reactive withthe other components of the reaction mixture, by scrubbing out said acidsubstantially as fast as it is formed with a spray of water.

covering an unsaturated organic chloride. WILLIAM ENGS. ARTHUR REDMOND.

